In recent years, there has been proposed manufacture of a package (electronic component) called fan out wafer level package (FOWLP) in which a re-distribution layer is formed instead of a wiring board. In the manufacture of the FOWLP, a semiconductor chip is sealed with a sealing resin. Then, a circuit forming surface of a semiconductor chip is exposed. A re-distribution layer is formed on that circuit forming surface (re-distribution forming step). In this manner, a re-distribution region is widely ensured.
The re-distribution layer is configured by stacking wiring layers while sandwiching an interlayer insulating film therebetween. The different wiring layers are electrically connected through copper via-holes provided in the interlayer insulating film. For example, copper via-holes or copper wires are formed by forming a photoresist pattern having via-holes or trenches on a metal layer and embedding copper in the via-holes or trenches by electroplating treatment (e.g., see Patent Literatures 1 and 2). The photoresist pattern having the via-holes or trenches is formed by exposing and developing a photoresist by using photolithography to thereby provide the via-holes or trenches in the photoresist.
In the past, via-holes are formed in a photoresist by a wet process using a developer. However, there is a demand for forming via-holes by a dry process. For example, at a step of forming copper via-holes, a copper layer, a titanium layer, and a mask including an organic resin layer are sequentially formed on a semiconductor substrate. Then, the titanium layer is subjected to plasma etching using a reactant gas including fluorine via the mask. In this manner, via-holes penetrating a layered film of the titanium layer and the organic resin layer are formed. Thereafter, copper is embedded in the via-holes by performing electroplating treatment. The copper via-holes are thus formed.
When the via-holes are formed by plasma etching using the reactant gas including fluorine, the surface of the organic resin layer (mask) is fluorinated and the fluoride is formed on the surface. When the surface of the organic resin layer is fluorinated, the surface of the organic resin layer exhibits hydrophobicity. It is thus difficult to cause an electroplating solution to enter the via-holes in subsequent electroplating treatment. It is difficult to obtain copper via-holes each having a desired shape. There is a fear that a wiring defect may occur.